expand: Keep track of semicoloned builtin macros

expand: Keep track of semicoloned builtin macros

This is quite a rough fix (like a lot of the macro expansion code...) but
it allows built-in macros to be treated as statements. I *think* asm!()
might be the only one where it really matters, but also doing something
like

{
    line!();
}

will now work, whereas before the macro invocation would not get expanded
properly and would be ignored.

gcc/rust/ChangeLog:

	* ast/rust-ast-fragment.h: Pass `is_semicolon` information to builtin
	macro transcribers.
	* ast/rust-macro.h: Pass semicolon information to transcriber..
	* expand/rust-macro-builtins-asm.cc (MacroBuiltin::asm_handler): Likewise.
	(parse_asm): Likewise.
	* expand/rust-macro-builtins-asm.h (parse_asm): Likewise.
	* expand/rust-macro-builtins-format-args.cc (MacroBuiltin::format_args_handler): Likewise.
	* expand/rust-macro-builtins-include.cc (MacroBuiltin::include_bytes_handler): Likewise.
	(MacroBuiltin::include_str_handler): Likewise.
	(MacroBuiltin::include_handler): Likewise.
	* expand/rust-macro-builtins-location.cc (MacroBuiltin::file_handler): Likewise.
	(MacroBuiltin::column_handler): Likewise.
	(MacroBuiltin::line_handler): Likewise.
	* expand/rust-macro-builtins-log-debug.cc (MacroBuiltin::assert_handler): Likewise.
	* expand/rust-macro-builtins-utility.cc (MacroBuiltin::compile_error_handler): Likewise.
	(MacroBuiltin::concat_handler): Likewise.
	(MacroBuiltin::env_handler): Likewise.
	(MacroBuiltin::cfg_handler): Likewise.
	(MacroBuiltin::stringify_handler): Likewise.
	* expand/rust-macro-builtins.cc (format_args_maker): Likewise.
	(inline_asm_maker): Likewise.
	(MacroBuiltin::sorry): Likewise.
	(MacroBuiltin::proc_macro_builtin): Likewise.
	* expand/rust-macro-builtins.h: Likewise.
	* expand/rust-macro-expand.cc (MacroExpander::expand_decl_macro): Likewise.
	(MacroExpander::expand_invoc): Likewise.
	* ast/rust-ast-visitor.cc (DefaultASTVisitor::visit): Remove rust_unreachable.
	* ast/rust-ast.cc (InlineAsm::accept_vis): Likewise.
	* hir/tree/rust-hir.cc (InlineAsm::accept_vis): Likewise.